The invention relates to valves for metering liquid (more or less viscous), or powdery products, some of which may actually exhibit dynamic flow behaviour similar to liquids.
Metering of such products appears to be necessary in many fields. In this case, the applicant was confronted in the field of bakery, with the problem of metering yeast as a liquid. Although this is the preferred field of application of the present invention, the latter cannot be limited to this field.
More particularly, the product to be metered may be a more or less thick yeast cream, this cream may notably be stable or stabilized, fresh, for example for use in bakery (the dry material content being for example comprised between 12 and 25%). This may also be a leaven as a liquid, a liquid (relatively viscous) yeast cream, a breadmaking enhancer as a liquid or powder after re-suspension. Combinations of such products may also be contemplated: this may thus be a yeast cream incorporating one or more breadmaking enhancers, such as enzymatic preparations, emulsifiers, etc.
Products of this type are presented in detail in the international application published under number WO 2004/048253 and in European patent EP0792930B1, and to which reference may be made.
As for powdery products, these may be a dry product comprising fine particles, of the dry yeast type (comprising from 90 to 95% of dry materials), or a breadmaking enhancer as a powder, the fluidity of which is sufficient for allowing it to be distributed through valves.
A metering valve of a known type presently used by the applicant is illustrated in FIG. 1 stated as “PRIOR ART”. This valve, integrated to a device complying with the aforementioned international application WO 2004/048253, comprises at an upper end, an endpiece for its connection to tubing for feeding the liquid (mounted on a bag-in-box itself stored in a cooled compartment of a machine for dispensing yeast cream), this endpiece being fitted into a tubular flex, currently made in silicone, a lower end of which is capable of being nipped elastically, by a translationally displaceable finger, between a release position (in solid line) in which it leaves the flex open to allow flow of the liquid, and a closed-up position (in dotted lines) in which it is brought back elastically in order to nip the flex and thereby prevent flow.
This valve has been thoroughly tested and has the advantage of simplicity of design. Nevertheless, it was shown that under the action of friction and nipping exerted by the metering finger, early wear may result in perforation of the flex.
Further, it was also shown that a portion of the product adheres to the inner wall of the flex above the nipping area, to form a deposit which firstly affects the general hygiene of the valve (not only by promoting bacterial development, but also by attracting insects), and secondly causes yellowing of the flex (to the detriment of the aesthetical aspect), which flex has to be replaced too frequently.
The invention notably aims at finding a remedy to these problems, by proposing among other objects, a metering valve of a novel type, which i.a., has enhanced seal, hygiene and durability properties.
For this purpose, according to a first object, the invention provides a valve for metering a liquid or powdery product, which comprises:                a fixed conduit for feeding the product, which has an upper end conformed as an endpiece for its connection to tubing for feeding the product, and a lower end for dispensing the product, this conduit defining at its lower end, an aperture for letting through the product;        a closure member positioned at the lower end of the conduit;        a coaxial sleeve mounted on the outside of the conduit, which has a lower end conformed as a valve seat, this sleeve delimiting together with the conduit, at its lower end, a chamber into which said aperture opens, said sleeve being translationally displaceable relatively to the conduit between a so-called closed position in which the valve seat tightly cooperates with the closure member, and a so-called open position in which the valve seat is spaced apart from the closure member in order to allow the product to flow.        
In the closed position of the sleeve, the product is prevented from flowing. With the intimate contact between the closure member and the valve seat, leaks may be avoided, and a good seal of the valve and good hygienic conditions are thereby guaranteed.
According to a particular embodiment, the valve seat is frusto-conical, whereas the closure member is for example of a hemispherical shape (it may also be conical or frusto-conical); this closure member may be made in an elastomeric material (preferably of the type for food). This closure member may also comprise an O-ring seal positioned in a peripheral groove of the closure member. Such a closure member is advantageous notably in that it provides a better seal to the product to be metered under pressure.
Moreover, a return spring is preferably provided for permanently urging the sleeve towards its closed position.
According to an embodiment, the chamber is delimited firstly by the valve seat and secondly by a seal ring, interposed between the conduit and the sleeve.
A bayonet mechanism may further be provided in order to ensure blocking of the sleeve in the open and/or closed position; this bayonet mechanism for example comprises a lug which cooperates with an angled groove.
According to a second object, the invention provides a device for metering a liquid or powdery product, which comprises a valve of the type described above and means for actuating this valve.
These means for actuating the valve for example comprise a fixed plate which may be provided with means for positioning the valve, and an actuation lever, pivotally mounted on the plate and which cooperates with the sleeve to control its displacement relatively to the conduit.
According to an embodiment, the lever has a flared notch by which the conduit may be introduced in order to ensure positioning of the endpiece relatively to the plate. The lever is preferably designed so as to be able to adopt a so-called “non operational” position in which it is spaced apart from the sleeve.
According to a third object, the invention provides a machine for dispensing a liquid or powdery product, which comprises:                a fixed structure provided with a compartment,        an interchangeable reservoir, positioned in said compartment and containing said product, this reservoir being provided with tubing for the flow of the product, and        a metering device as described above,        in which the valve is connected on said reservoir, its conduit being connected to the tubing via its endpiece, whereas the actuation means are mounted on the fixed structure.        
According to a fourth object, the invention provides a machine for dispensing a liquid or powdery product, which comprises:                a fixed structure provided with a compartment and having a notch for introducing the valve,        an interchangeable reservoir, positioned in said compartment and containing said product, this reservoir being provided with tubing for the flow of the product, and        a metering device according to the embodiment described above,        a machine in which the plate is mounted on the fixed structure in the vicinity of the notch, and in which the valve is set into place on the fixed structure while being positioned in the notch and connected onto said reservoir, its conduit being connected to the tubing via its end piece.        
According to a fifth object, the invention provides an installation for dispensing a liquid product which includes:                a container containing said liquid product;        means for dispensing a liquid product, connecting the container to the metering valve having features like those mentioned earlier;        a pump with which the liquid product of the container may be withdrawn and said liquid product may be circulated in the liquid product dispensing means;        a metering device with the features described earlier.        
According to a preferential embodiment, and in order to allow a liquid product circulation loop to be formed, the liquid product dispensing means comprise a return conduit starting from upstream of the metering valve and opening out either into the container, or into a secondary conduit.
According to a preferential embodiment, and in order to allow cleaning of the conduits in which the liquid product flows, the installation comprises a reservoir of cleaning solution capable of cleaning the means for dispensing the liquid product.
According to a preferential embodiment, and in order to allow a cleaning loop to be formed which passes through the metering valve, the installation comprises a flexible connecting pipe capable of being connected onto the valve.
According to a preferential embodiment, the flexible connecting pipe opens out either into the cleaning solution reservoir, or into a connecting point provided on the return conduit, in a conduit opening out into the cleaning solution reservoir. An advantageous installation according to the invention may comprise one or more of these preferential embodiments, i.e., the conduit for returning the liquid product to be metered, a cleaning solution reservoir and/or the flexible connecting pipe.
An installation according to the invention may further comprise one or more metering devices in parallel, with or without a cleaning loop, and with or without a loop for returning the liquid product into the container.
An installation comprising several metering devices, a cleaning loop for cleaning the valves in series and a loop for returning liquid product into the container, is particularly advantageous in that it allows a same cleaning flow rate in the whole installation.
Advantageously, the secondary conduit opens out into the cleaning solution reservoir.
The object of the invention is also the use of the metering valve and/or the metering device and/or the dispensing machine and/or the dispensing installation as described earlier, in bakeries, and more particularly for metering the bakeries' liquid yeast cream.
Other objects and advantages of the invention will become apparent in the light of the description made hereafter with reference to the appended drawings.